March 28, 2012

Alder Eradication in Orari Gorge in Sight

Environment Canterbury is on target to totally eradicate a highly invasive tree species from the upper Orari River catchment.

Alder, an introduced tree, has spread extensively through the Orari Gorge. It grows prolifically not just in the river bed itself, but in recent years has begun to colonise adjacent banks and hillsides.

Environment Canterbury’s South Canterbury river engineering team has been tackling the alders for nearly a decade using ground spraying and helicopter boom spraying.

However during this last growing season, the team has had additional funding from the council’s biodiversity strategy funding scheme. This scheme aims to restore, preserve and protect an area’s biodiversity. The extra funding has enabled the team to implement an even more effective approach in tackling the alders.

“We’ve been using a helicopter with one of our team members targeting individual trees using a gun spray. This has enabled us to work in some of the more inaccessible areas of the gorge more effectively,” Timaru-based Area Engineer Bruce Scarlett says. “As a result we’re now confident we are not talking about controlling alder in the Orari Gorge but eradicating it completely.”

“Alders can grow up to eight metres tall and seed prolifically so we need to be able to get to all of them if we’re to succeed. They not only choke up the river beds, which can lead to flooding, but they threaten the natural biodiversity of the river and its environs.”

Mr Scarlett expects that the total eradication of the alders could take a few more years while the remaining less accessible trees and seedlings are systematically removed.

ENDS

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